Radio receiver circuit



E. BRUCE 1,913,428

RADIO RECEIVER CIRCUIT June 13, 1933.

Filed March 14, 1929 2/ IVTERMED/ATE FREQUENCY F/LTER AND 9 AMPLIFIER 0INVENTOH E. Bgucs JfMea ATTURNE Y Patented June 1 3, 1933 UNITED STATESPA FI E EDMQNDB I C F un BANK, i rwwzraasnr. ASSIGNQB To rent rename useRAT S, meQ i RAIE-D, Ne Y K Y a corr ra'rmn o NEWLYQBK.

same RECEIVER erra um Application med March 14, r929, Serial nofeeassrThis invention relates to radio receiving circuits and hasfor an obi ectto reduce the effects of fading, that is, variations in intensity of thereceived wave. 1 .5 a specific embodiment ofthis invention a pluralityof geographically separated antennae are arranged to receive waves fromthe same transmitter. a

V detector is associated with each ofthe antennae andthe receivedwavesare combined impressed upon a low frequency detector'in Whichtheyare detected to yield thesignal. A resistance element is included in thel plate circuit of the low frequency detector and the grid biasingpotentials of the high frequency detectors are controlled by thedire ctcurrent potential drop across this resistance;

The high frequency detectors are operated near the critical points oftheir grid potentialplate currentcharacteristics, so thatany materialincrease in the negative grid bias will render them inoperative forincoming Waves of small amplitude. a a i The biasing potential due tothe drop across the resistance in the low frequency detector will bedeterminedat any instant by thesignal fromthe antenna inwhichtheoutput'has the largest amplitude and will block thecdeteetersassociated with those antennae in which the amplitude of the output ismaterially sinaller. i 1 InZthe drawingthere isshownoneembodiment of theinvention in a system employing three antennae 1,2 and 3 which areassociated withthe high frequency. detectors 4,5 and 6, respectively, ofthe electric discharge or audiontype. a j i :Ccupling to the :inputs ofthe detectors is provided through the step-up auto+trans formers 7, 8and9 connected across which are the tuning condensers 10, 11, and .12.One secondary terminalof each of the transformers 7 8 and 9 is connected11 01 17118 gr-id of the .correspondingdetector. The common. primaryandsecondary terminals of the transformers are connected togetherandthrough the blockingconc lenser 13 to the groundfor thecommon cathodecircuit of the detectors. a

a The anodes of thedetectors are connected together andto one terminalof the primary winding of the transformerll. The other terminal of thisWinding is connected through the secondary of transformer 15 and thespace cur-rentbattery 16 to the common cathode cirsuit to the detectors.A heterodyne wave is supplied from the oscillator 17 to the anodecircuit of the detectorsthrough the trans former 15. V i i The secondarywinding of the transformer 14 is connected to the inputterminals'o f anintermediate frequency filter and amplifier 18, The outputof theamplifier 18 is connected to the grid circuit of a low frequencydetector herein shown, by way of'example, as an electric or spacedischarge device 19. The output or anodeicircuit of the detectorcomprises in series, the space current battery 20, receiver 21 andresistance element 22.

the resistance 22by the output current ofthe detector 19, that potentialprovidinga negatiivebias for the detectors 4, 5and6 which isproportional to the rectified current flowingthrough the output circuitof detector 19.

Theibattery, 24 supplies a normal biasing potentialto the gridsof tubes4, 5 and 6.

:The antennae l, 2Qand 3 and the associated resonant circuits 7+10, 8-11and 9-12are designed and adjusted :to receive the wave from, onetransmitter. The antennae are so arranged geographicallythat fadingconditions-at each varydifferently. V

The ireceiyed waves are impressed on the grids ofgtherespectivedetectors at, 5 and6 and are combined in the common anode circuit withoscillations supplied by the local oscillator 17 The resultantintermediate frequency waves are amplified in the amplifier 18 andimpressed on the low frequency detector 19, wherein they are detected toyield the signal wave.

The system is so designed, particularly with regard to the choice ofvoltage from the biasing battery 2d-and control voltage supplied-by theresistance 22, that a wave of any material amplitude received in any ofthe antennae 1, 2 or 3 will impress through the control connection 23such a negative potential upon the grids of detectors 4 and 5, 4 and 6,or 5and 6, as the case may be, as to block them for waves ofvsubstantially smaller amplitude. Thus the system will operate so that atany instant the antenna receiving the wave of largest amplitude will bethe only one which will supply a wave through the circuit to thereceiver 21, the high frequency detectors associated with the otherantennae being rendered inoperative by the action of the controlconnection 23 to prevent the transmission of waves through them.

While the invention is herein illustrated in one specific embodiment, itis obvious that it is capable of various modifications which willreadily suggest themselves to those skilled in the art.

What is claimed is:

7 1. In combination, a plurality of antennae, an electric dischargedevice coupled to each of said antennae to received waves therefrom,means for producing a control potential which is a function of theamplitude of the wave output from each of said devices, and meansresponsive to said potential for controlling said devices to renderinoperative at least for the transmission of waves of small amplitudethose in which the amplitude of the received wave is small compared tothat of the received wave in another.

7 2. In combination, a plurality of antennae so arranged that thereception conditions vary differently at each, a circuit including anelectric discharge device so adjusted that said device operates near thecritical point of its transmission characteristic coupled to each ofsaid antennae, means for producing a unidirectional potential which is afunction of the amplitude of the wave received in each of said antennae,and means responsive to said potential for controlling said dischargedevices to render inoperative for the transmission of waves of amplitudeof the order of those received in the respective antennae those of saiddevices in which the amplitude of the received wave is small compared tothat of the received wave in another of said devices. I

3. In combination, a plurality of antennae, an electric discharge devicecoupled to each of said antennae to receive waves therefrom,

means in circuit with said devices for reducing the frequency of thereceived waves, and means for producing a unidirectional potential whichis a function of the amplitude of the reduced frequency wave, and meansresponsive to said potential for controlling the operation of saiddischarge devices to render inoperative for the transmission of waves ofamplitude of the order of those received in the respective antennaethose devices in which the amplitude of the received wave is smallcompared to the received wave in another.

4. A radio receiving system comprising a plurality of antennae, a localsource of oscillations, an electric discharge detector coupled to eachof said antennae for combining the received wave with the localoscillations, said detectors having transmission characteris tics withcritical points at which the devices are substantially inoperative forthe transmission of waves of small amplitude being operated near saidcritical points of their characteristics, an intermediate frequencyamplifier connected to selectively repeat the detected waves from saiddetectors, an electric discharge detector for detecting the Waves fromsaid intermediate frequency ainplifier, means for producing aunidirectional potential proportional to the direct current outputcurrent of the last mentioned detector, and means for impressing saidunidirectional potential between the electrodes of the first mentioneddetectors to render inoperative forthe transmission of waves of smallamplitude those in which the amplitudes of the received waves are smallcompared to that of the received wave in an other of said detectors.

5. The method of operating a radio receiving system having plurality ofantennae and an electric discharge device coupled to each antenna, whichcomprises producing a unidirectional potential which is a function ofthe amplitude of the wave of largest amplitude received at any instantin any of said devices, and utilizing said potential to so affect thedischarge devices in which the received waves are of substantiallysmaller amplitude that they are rendered substantially inoperative forthe transmission of waves of said small amplitude.

6. The method of radio reception which comprises receiving at aplurality of separate points, waves carrying the same signal, changingthe frequency of the received waves, detecting the waves of changedfrequency, producing from the detected waves a unidirectional potential,and controlling in accordance with said potential, the transmission ofthe received waves to substantially suppress" all but that one of thereceived' waves having at any instant the largest amplitude. v

7. Aradio receiver comprising a plurality of antennae so. located thatfading conditions vary differently at each, frequency changing meansincluding an electric discharge modulator coupled to each antenna toreduce the frequency of the received waves, means for selectivelyamplifying the waves of reduced frequency to the substantial exclusionof waves of higher frequency, and means for detecting the selectivelyamplified waves to produce waves of signal frequency, the detectingmeansbeing provided with connectlOHS to said electricvdischarge modulators toapply thereto a voltage of such magnitude and sign as to rendersubstantially inoperative for the translating of waves of smallamplitude the modulators receiving waves of substantially smalleramplitude than the Waves received in another of the modulators.

8. In combination, a plurality of antenna so related to each other thatthe received waves vary differently at the several receivers withvariationsin transmission conditions that reception conditionsvarydifferently at i each, a plurality of electric discharge devices eachhaving an anode, a cathode and a control element, means for supplyingthe waves received in each of said antennae to a .corresponding one ofsaid devices, means for pro ducing a unidirectional electromotive forcehaving at any instant an amplitude which is function of the amplitude ofthe received waves, means for impressing said electromotive forceupon'the control electrodes ofsaid devices to so affect the transmissioncharacteristics thereofthat those devices WlllCh the instant arereceiving waves of sub stantially lower amplitudes than the wavesbeingreceived by another device are rendered substantially inoperativefor the trans mission of waves of said lower amplitudes, and a signalreceiving circuit connected to receive waves transmitted by any of saiddevices.

9. In a signaling system subgect to variable transmission conditions, aplurality of receivers each receiving the same signal and so related toeach other that the received signals vary differently at the severalreceivers with variations in transmission conditions, a signal circuitcommon to said receivers, and means responsive to the amplitude of theoutputs of saidreceivers for automatically controlling the gain of atleast one i of said receivers to. render substantially ina operativesaid one of said receivers when its output is materially lower than thatof another of said receivers.

10. In a signaling system subject to variable transmissionconditions, aplurality of receivers each receiving the same signal and so related toeach other that the received signals vary differently at the severalreceivers with variations in transmission conditions, each receivercomprising an electric discharge device, a signal circuit common to saidreceivers, means for producing a uniof one of said receivers in responseto the amplitude of the signal received in at least one of the other ofsaid signal receivers to render substantially inoperative said one ofsaid receivers when the amplitude of the signal wave received thereby ismaterially lower than the amplitude of the signal Wave received by saidother of said signal receivers.

12. In a signaling system subject to variable transmission conditions, aplurality of receivers each receiving the same signal and so related toeach other that the received signals. varydiiierently at the severalreceivers with variations in transmission conditions, and means forautomatically controlling over a continuous rangethe gain of at leastone of said receivers in response to the amplitude of the signalreceived in at least one of the respective others of said signalreceivers to render substantially inoperative said one of said receiverswhen the amplitude of the signal wave received thereby is materiallylower than the amplitude of the signal received by said one of therespective others of said signal receivers.

13. In combination, a plurality of radio signal receivers, means forcombining the sig nal output of said receivers,and means forautomatically controlling over a continuous range the gain of one ofsaid receivers in response to the amplitude of the signal from saidmeans for combining the signal output of said receivers to rendersubstantially inoperative said one of said receivers when the amplitudeof the signal Wave received thereby is materially lower than theamplitude of the signal wave received by another of said signalreceivers.

In witness whereof, I hereunto subscribe my name this 12th day of March,1929. y

EDMOND BRUCE.

DISCLAIMER 1,913,428.Edm0nd Bruce, Red Bank, N. J. RADIO RECEIVERCIRCUIT. Patent dated June 13, 1933. Disclaimer filed January 18, 1935,by the assignee, Bell Telephone Laboratories, Incorporated.

Hereby enters this disclaimer to the subject-matter of the said claimsof said Letters Patent which are in the following words to wit:

1. In combination, a plurality of antennae, an electric discharge devicecoupled to each of said antennae to receive waves therefrom, means forproducing a control potential which is a function of the amplitude ofthe wave output from each of said devices, and means responsive to saidpotential for controlling said devices to render inoperative at leastfor the transmission of waves of small amplitude those in which theamplitude of the received wave is small compared to that of thereceived. wave in another.

5. The method of operating a radio receiving system having a pluralityof antennae and an electric discharge device coupled to each antenna,which comprises producing a unidirectional potential which is a functionof the amplitude of the wave of largest amplitude received at anyinstant in any of said devices, and utilizing said potential to soaffect the discharge devices in which the received waves are ofsubstantially smaller amplitude that they are rendered substantiallyinoperative for the transmission of waves of said small amplitude.

6. The method of radio reception which comprises receiving at aplurality of separate points, waves carrying the same signal, changingthe frequency of the received waves, detecting the'waves of changedfrequency, producing from the detected waves a unidirectional potential,and controlling, in accordance with said potential, the transmission ofthe received waves to substantially suppress all but that one of thereceived waves having at any instant the largest amplitude.

8. In combination, a plurality of antennae so related to each other thatthe received waves vary differently at the several receivers withvariations in transmission conditions that reception conditions varydifferently at each, a plurality of electric discharge devices eachhaving an anode, a cathode and a control element, means for supplyingthe waves received in each of said antennae to a. corresponding one ofsaid devices, means for producing a unidirectional electromotive forcehaving at any instant an amplitude which is a function of the amplitudeof the received waves, means for impressing said electromotive forceupon the control electrodes of said devices to so affect thetransmission characteristics thereof that those devices which at theinstant are receiving Waves of substantially lower amplitudes than thewaves being received by another device are rendered substantiallyinoperative for the transmission of waves of said lower amplitudes, anda signal receiving circuit connected to receive waves transmitted by anyof said devices.

9. In a signaling system subject to variable transmission conditions, aplurality of receivers each receiving the same signal and so related toeach other that the received signals vary differently at the severalreceivers with variations in transmission conditions, a signal circuitcommon to said receivers, and means responsive to the amplitude of theoutputs of said receivers for automatically controlling the gain of atleast one of said receivers to render substantially inoperative said oneof said receivers when its output is materially lower than that ofanother of said receivers.

10. In a signaling system subject to variable transmission conditions, aplurality of receivers each receiving the same signal and so related toeach other that the received signals vary diflercntly at the severalreceivers with variations in transf mission conditions, each receivercomprising an electric discharge device, a signal circuit common to saidreceivers, means for producing a unidirectional potential which is afunction of the amplitude of the input to said signal circuit, and meansfor impressing said unidirectional potential between the electrodes ofsaid electric discharge devices to render inoperative those of saiddevices in which the amplitude of the received wave issmall comparedwith that of the received wave in another of said devices.

11. In combination, a plurality of signal receivers, and means forautomatically controlling over acontinuous range the gain of one of saidreceivers in response to the amplitude of the signal received in atleast one of the other of said signal receivers to render substantiallyinoperative said one of said receivers when the amplitude of the signalwave received thereby is materially lower than the amplitude of thesignal wave received by said other of said signal receivers.

12. In a signaling system subject to variable transmission conditions, aplurality of receivers each receiving the same signal and so related toeach other that the received signals vary differently at the severalreceivers with variations in transmission conditions, and means forautomatically controlling over a continuous range the gain of at leastone of said receivers in response to the amplitude of the signalreceived in at least one of the respective others of said signalreceivers to render substantially inoperative said one of said receiverswhen the amplitude of the signal wave received thereby is materiallylower than the amplitude of the signal received by said one of therespective others of said signal receivers.

13. In combination, a plurality of radio signal receivers, means forcombining the signal output of said receivers, and means forautomatically controlling over a continuous range the gain of one ofsaid receivers in response to the amplitude of the signal from saidmeans for combining the signal output of said receivers to rendersubstantially inoperative said one of said receivers when the amplitudeof the signal wave received thereby is materially lower than theamplitude of the signal wave received by another of said signalreceivers.

. [Ofiicial Gazette February 12, 1985.]

